Prefilled syringes are commonly prepared and sold so the syringe does not need to be filled before use. The syringe can be prefilled with saline solution, a dye for injection, or a pharmaceutically active preparation, for some examples.
Commonly, the prefilled syringe is capped at the distal end, as with a cap, and is closed at the proximal end by its drawn plunger. The prefilled syringe can be wrapped in a sterile package before use. To use the prefilled syringe, the packaging and cap are removed, optionally a hypodermic needle or another delivery conduit is attached to the distal end of the barrel, the delivery conduit or syringe is moved to a use position (such as by inserting the hypodermic needle into a patient's blood vessel or into apparatus to be rinsed with the contents of the syringe), and the plunger is advanced in the barrel to inject the contents of the barrel.
One important consideration in manufacturing pre-filled syringes is that the contents of the syringe desirably will have a substantial shelf life, during which it is important to isolate the material filling the syringe from the barrel wall containing it, to avoid leaching material from the barrel into the prefilled contents or vice versa.
Since many of these vessels are inexpensive and used in large quantities, for certain applications it will be useful to reliably obtain the necessary shelf life without increasing the manufacturing cost to a prohibitive level. It is also desirable for certain applications to move away from glass vessels, which can break and are expensive to manufacture, in favor of plastic vessels which are rarely broken in normal use (and if broken do not form sharp shards from remnants of the vessel, like a glass tube would). Glass vessels have been favored because glass is more gas tight and inert to pre-filled contents than untreated plastics. Also, due to its traditional use, glass is well accepted, as it is known to be relatively innocuous when contacted with medical samples or pharmaceutical preparations and the like.
A further consideration when regarding syringes is to ensure that the plunger can move at a constant speed and with a constant force when it is pressed into the barrel. For this purpose, a lubricity layer, either on one or on both of the barrel and the plunger, is desirable.